Process for making a nonwoven fabric of needling, heating, burnishing and cooling

Abstract

A process is provided for making strong, permeable nonwoven fabrics having an abrasion-resistant burnished surface. The process involves providing a lightly consolidated or weakly bonded web of thermoplastic synthetic organic fibers, needle punching the web, heating a surface of the needled web, and burnishing the heated surface with a rotating, smooth-surfaced metal roll, which preferably simultaneously cools the web surface.

We claim: 
     
       1. A process for preparing a strong, permeable nonwoven fabric having an abrasion-resistant surface, the process comprising (a) providing a lightly consolidated web of thermoplastic, synthetic organic fibers, the web having a unit weight in the range of 75 to 150 grams/square meter, the fibers having a dtex in the range of 1.5 to 15 and at least a minor portion of the fibers having melting temperatures in the range of 160° to 190° C., (b) needle-punching the web to form 30 to 150 penetrations/square centimeter, (c) heating at least one surface of the needled web to a temperature of at least 140° C., (d) burnishing the heated surface of the web with a rotating, smooth-surfacted metal roll and (e) cooling the burnished web. 
     
     
       2. A process of claim 1 wherein the roll rotates with a peripheral velocity of at least 25 meters/minute relative to the web, is maintained in intimate frictional contact with the web for at least one second and simultaneously burnishes and cools the heated, needled web. 
     
     
       3. A process of claim 1 or 2 wherein the lightly consolidated web comprises substantially continuous filaments of isotactic polypropylene, the surface of the needled web is heated to a temperature in the range of 145° to 156° C. and the roll surface is maintained at a temperature of lower than 60° C. 
     
     
       4. A process of claim 1 or 2 wherein the lightly consolidated web comprises a major portion of substantially continuous filaments of poly(ethylene terephthalate) homopolymer and a minor portion of substantially continuous filaments of poly(ethylene terephthalate/isophthalate) copolymer, the needled web is heated to a temperature in the range of 195° to 210° C. and the roll surface is maintained at a temperature of lower than 90° C. 
     
     
       5. A nonwoven fabric having an abrasion-resistant burnished surface, the fabric comprising substantially continuous filaments of synthetic organic polymer of 1.5 to 15 dtex and having a unit weight of 75 to 150 g/m 2 , a sheet grab tensile strength of at least 220 Newtons, a trapezoidal tear strength of at least 100 Newtons, an elongation at 4.54 kg load of 6 to 13%, and a Frazier air permeability of at least 90 m/min. 
     
     
       6. A nonwoven fabric of claim 5 wherein the filaments are of isotactic polypropylene polymer. 
     
     
       7. A nonwoven fabric of claim 5 wherein the filaments are of polyester polymer.